The SiS 85C496/497 486 Green PC VESA/ISA/PCI Chipset has support for PCI
steering and the ELCR register implemented. These features are handled
by the SiS85C497 AT Bus Controller & Megacell (ATM) ISA bridge, however
the device is wired as a peer bridge directly to the host bus and has
its PCI configuration registers decoded at addresses 0x80-0xff by the
accompanying SiS85C496 PCI & CPU Memory Controller (PCM) host bridge[1].
Therefore we need to match on the host bridge's vendor and device ID.
Like with the SiS85C503 PIRQ router handle link value ranges of 1-4 and
0xc0-0xc3, corresponding respectively to PIRQ line numbers counted from
1 and link register PCI configuration space addresses.
References:
[1] "486 Green PC VESA/ISA/PCI Chipset, SiS 85C496/497", Rev 3.0,
Silicon Integrated Systems Corp., July 1995, Part IV, Section 3.
"PCI Configuration Space Registers (00h ~ FFh)", p. 114
Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx>
Tested-by: Nikolai Zhubr <zhubr.2@xxxxxxxxx>
---
arch/x86/pci/irq.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 80 insertions(+)
linux-x86-pirq-router-sis85c497.diff
Index: linux-macro/arch/x86/pci/irq.c
===================================================================
--- linux-macro.orig/arch/x86/pci/irq.c
+++ linux-macro/arch/x86/pci/irq.c
@@ -580,6 +580,81 @@ static int pirq_cyrix_set(struct pci_dev
return 1;
}
+
+/*
+ * PIRQ routing for the SiS85C497 AT Bus Controller & Megacell (ATM)
+ * ISA bridge used with the SiS 85C496/497 486 Green PC VESA/ISA/PCI
+ * Chipset.
+ *
+ * There are four PCI INTx#-to-IRQ Link registers provided in the
+ * SiS85C497 part of the peculiar combined 85C496/497 configuration
+ * space decoded by the SiS85C496 PCI & CPU Memory Controller (PCM)
+ * host bridge, at 0xc0/0xc1/0xc2/0xc3 respectively for the PCI INT
+ * A/B/C/D lines. Bit 7 enables the respective link if set and bits
+ * 3:0 select the 8259A IRQ line as follows:
+ *
+ * 0000 : Reserved
+ * 0001 : Reserved
+ * 0010 : Reserved
+ * 0011 : IRQ3
+ * 0100 : IRQ4
+ * 0101 : IRQ5
+ * 0110 : IRQ6
+ * 0111 : IRQ7
+ * 1000 : Reserved
+ * 1001 : IRQ9
+ * 1010 : IRQ10
+ * 1011 : IRQ11
+ * 1100 : IRQ12
+ * 1101 : Reserved
+ * 1110 : IRQ14
+ * 1111 : IRQ15
+ *
+ * We avoid using a reserved value for disabled links, hence the
+ * choice of IRQ15 for that case.
+ *
+ * References:
+ *
+ * "486 Green PC VESA/ISA/PCI Chipset, SiS 85C496/497", Rev 3.0,
+ * Silicon Integrated Systems Corp., July 1995
+ */
+
+#define PCI_SIS497_INTA_TO_IRQ_LINK 0xc0u
+
+#define PIRQ_SIS497_IRQ_MASK 0x0fu
+#define PIRQ_SIS497_IRQ_ENABLE 0x80u
+
+static int pirq_sis497_get(struct pci_dev *router, struct pci_dev *dev,
+ int pirq)
+{
+ int reg;
+ u8 x;
+
+ reg = pirq;
+ if (reg >= 1 && reg <= 4)
+ reg += PCI_SIS497_INTA_TO_IRQ_LINK - 1;
+
+ pci_read_config_byte(router, reg, &x);
+ return (x & PIRQ_SIS497_IRQ_ENABLE) ? (x & PIRQ_SIS497_IRQ_MASK) : 0;
+}
+
+static int pirq_sis497_set(struct pci_dev *router, struct pci_dev *dev,
+ int pirq, int irq)
+{
+ int reg;
+ u8 x;
+
+ reg = pirq;
+ if (reg >= 1 && reg <= 4)
+ reg += PCI_SIS497_INTA_TO_IRQ_LINK - 1;
+
+ pci_read_config_byte(router, reg, &x);
+ x &= ~(PIRQ_SIS497_IRQ_MASK | PIRQ_SIS497_IRQ_ENABLE);
+ x |= irq ? (PIRQ_SIS497_IRQ_ENABLE | irq) : PIRQ_SIS497_IRQ_MASK;
+ pci_write_config_byte(router, reg, x);
+ return 1;
+}
+
/*
* PIRQ routing for SiS 85C503 router used in several SiS chipsets.
* We have to deal with the following issues here:
@@ -969,6 +1044,11 @@ static __init int serverworks_router_pro
static __init int sis_router_probe(struct irq_router *r, struct pci_dev *router, u16 device)
{
switch (device) {
+ case PCI_DEVICE_ID_SI_496:
+ r->name = "SiS85C497";
+ r->get = pirq_sis497_get;
+ r->set = pirq_sis497_set;
+ return 1;
case PCI_DEVICE_ID_SI_503:
r->name = "SiS85C503";
r->get = pirq_sis503_get;
